A city slicker decided to buy himself a pig, so he drove to the country until he saw a sign that said "PIGS FOR SALE".
Turning into the driveway, he spotted the farmer, told him what he wanted, and they agreed on a price. They went to the barn where the farmer picked up a pig by the tail with his teeth. "Yup, that there swine weighs 74 pounds."

Noticing the man's bewilderment, the farmer explained that it was a family trait, passed on through generations, to be able to precisely weigh pigs in that manner. The city slicker, however, insisted on a second opinion. So the farmer called his son over and the boy came up with the same result. The man was ready to buy the pig on the spot, but the farmer said to go on up to the house and pay his wife. The man could then bring the receipt back to the farmer and take the pig. After a long wait, the city slicker finally returned, but without a receipt.

"What's the problem, son?" asked the farmer.
"I went up there like you said," said the man, "And your wife was too busy."
"Busy doing what?"
"Well, don't quote me on this," he warned, "But I think she was weighing the milkman."